Older LUX Natural Gas/Central AC system, LUX 4 wire (Green, Yellow, White, Red)(RedH and RedC are jumper-ed together) Thermostat, this past week the AC (Outside) and the blower (inside) would keep running even after the desired temp has been reached. Thinking that this was an issue with the t-stat, I purchased a new one from (LUX) Lowes, installed, set up and turned on. AC comes on, house starts to cool down. Desired temp is reached in the house and the cooling system keeps on running. If I turn off the unit at the t-stat, AC and Blower both turn off. Assuming that I give the system the t-stat controlled 5 min timeline and turn it back on, system comes back online and runs, and runs, and runs, and runs........ While this keeps the house at a nice penguin temp, for the humans in the home its getting a little chilly.

Any advice as to what to look at next, or what to test to see where the problem may be?